update_unicode.sh: set UNICODE_DIR only once
update_unicode.sh: set UNICODE_DIR only once

The value is the same on both uniset invocations, so "Don't Repeat
Yourself" applies.

Since this is done as the last command in the sequence, there's no
need to unset UNICODE_DIR at the end.

Signed-off-by: Beat Bolli <492283376763148288091dc1edb13b1b4edf3d1b@drbeat.li>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git